Hip fractures present significant healthcare issues. These healthcare issues includes mortality, morbidity and increased healthcare costs. Improvements to the rate of reliable healing would significantly benefit patient health and reduce healthcare costs.
Proximal fractures of the femur are traditionally treated with either (i) an intramedullary rod (sometimes referred to as an intramedullary nail) which is positioned in the intramedullary canal of the femur, or (ii) a plate applied to the side of the femur and fixed in place with one or more screws set into the femur. The choice of using an intramedullary rod or a plate and screw is generally based on the location and complexity of the fracture.
As noted above, the intramedullary rod is placed in the intramedullary canal of the femur and typically provides excellent mechanical stability for the bone. Among other things, the intramedullary rod exhibits good weight-sharing properties. However, the use of an intramedullary rod also involves a more complex surgical procedure and higher cost.
Plates such as the Dynamic Hip Screw (DHS) plate are generally simpler to deploy and less expensive than intramedullary rods. Plates generally work well for stable intertrochanteric fractures. However, in subtrochanteric fractures and unstable intertrochanteric fractures, it is difficult to achieve proper compression of the fracture site with plates upon the application of weight. Therefore, most subtrochanteric fractures and unstable intertrochanteric fractures are treated with intramedullary rods.
When the treatment of subtrochanteric fractures and unstable intertrochanteric fractures by intramedullary rods is unsuccessful, the fractures are typically treated with tension band plates (such as a tension band blade plate) which utilize the geometry of the femoral subtrochanteric region and the compressive forces imposed by the surrounding musculature. A tension band construct, by definition, utilizes tensile forces and converts them into compressive forces. At an advanced level, when a tension band blade plate is applied to the tension side of the femur and pressure is thereafter applied, the tension band blade plate converts the tension forces into compressive forces which can be used to stabilize the fracture. Tension band blade plates are known to be effective in treating proximal femoral fractures. However, installation of these tension band blade plates requires substantial technical skill and involves a more complex operation. Therefore, the use of tension band blade plates is generally not suited for index surgery (i.e., the first surgery performed after the occurrence of a fracture), and is best suited for revising failed fracture repairs.
It is believed that a device that can combine the mechanical advantages of intramedullary rods with the mechanical advantages of tension band blade plates would be extremely useful for treating all kinds of proximal femoral fractures, including not only the aforementioned subtrochanteric fractures and unstable intertrochanteric fractures, but also including stable intertrochanteric fractures and other types of proximal femoral fractures. Such a device would also be extremely useful for treating fractures of other bones in the body. For the sake of clarity, even though the present invention may be used for all hip fractures (including stable and unstable intertrochanteric fractures, subtrochanteric fractures, and other types of proximal femoral fractures), and even though the present invention may be used for fractures of other bones in the body, the following discussion of the present invention will focus on subtrochanteric fractures and unstable intertrochanteric fractures.
Intramedullary rods have evolved over time. The first generation of intramedullary rods essentially involved inserting a solid rod down the intramedullary canal of the femur. This type of intramedullary rod is relatively primitive and only grossly aligns the bone. The first generation of intramedullary rods does not control motion at the fracture line in any specific plane.
The second generation of intramedullary rods was the dynamic interlocking intramedullary rod. The dynamic interlocking intramedullary rod allows for compression of the bone at the fracture site by allowing axial compression of the fracture. This axial compression of the fracture is achieved through the use of lag screws which pass through the bone, across the intramedullary rod and back into the bone. However, existing lag screw constructs do not control the coronal plane motion of the unstable and subtrochanteric fractures. Studies have shown that the dynamic interlocking intramedullary rod has not been as effective as desired. More particularly, for the repair of subtrochanteric fractures and fractures of the femoral neck or femoral head using a dynamic interlocking intramedullary rod, the intramedullary rod is driven into the femur from the proximal end and a femoral neck pin is introduced into the femoral head via the femoral neck of the femur, with the femoral neck pin passing through a bore formed in the intramedullary rod at an oblique angle to the axis of the intramedullary rod. The dynamic interlocking intramedullary rod, when placed under a load, is subjected to a combined stress which is composed of compressive and tensile stresses and shear loads. In the case of delayed healing and overload, a crack or fissure may develop in the bone, namely at the site at which the highest shear stress occurs. Current dynamic interlocking intramedullary rods do not provide any kind of unique biomechanical advantage for fracture healing in unstable intertrochanteric and subtrochanteric fractures except acting as an intramedullary buttress. The dynamic interlocking intramedullary rod does not offer any anatomic site-specific advantage for healing of the fracture.
The present invention addresses this biomechanical problem by reducing the shear loads on the intramedullary rod and provides a more stable biomechanical environment for a more accelerated and reliable healing of the fracture.